Predictive soil sampling and analysis for the soybean cyst nematode (SCN) can provide timely information for growers, especially those considering planting soybeans this growing season. Growers can use the analysis to select SCN-management strategies and tactics that will minimize losses. Fields to sample might include those with an unexplained drop in yields of the last soybean crop or a history of stunted and perhaps yellowed soybeans in spots or patches. Growers may also want to sample to check nematode populations following 3- to 4-year rotations involving the use of nonhost crops and SCN-resistant varieties. This check is especially important when the initial population was determined to be at a moderate-to-high level (5 to above 25 cysts per 100 cc of soil).
Although a fall sampling may be preferable, samples can still be collected in early spring. However, you may find SCN for the first time and thus need to quickly change the crop or variety to be planted. So time is limited for this growing season.
Sampling procedures: For best results, take 12 to 24 subsamples (probes) in a zigzag pattern through each 10 to 20 acres to be sampled. Collect soil to a depth of 6 to 8 inches. Mix the soil and place approximately 1 quart in a sturdy plastic bag; repeat for each 10 to 20 set.
Next, complete a nematode soil sample form (available at your nearest Extension office) and submit it with the packaged samples. If no form is available, include an attached letter with (1) your name, address, county, and phone number; (2) any symptoms observed during previous plantings of soybeans and the patterns of the symptoms in the field (scattered, clustered in spots, or uniform); (3) the approximate size of the area sampled; (4) the cropping history for at least 3 years; (5) herbicides or other pesticides used the previous year; and (6) the crop or crops to be grown this season. Send them to Plant Pathology, N-533 Turner Hall, 1102 S. Goodwin Ave., Urbana, IL 61801. After May 3 send samples to the Plant Clinic, 1401 W. St. Mary's Road, Urbana, IL 61802.
For more information on sampling, refer to the Report on Plant Disease Nos. 1100 and 1107, available at Extension centers or from the Department of Crop Sciences (at the cost of $1.00 per copy) at the above-mentioned Turner Hall address.--Dale I. Edwards